Green synthesis of silver-containing nanocomposites based on polylactide (PLA) was carried out in two ways. With the use of green tea extract, Ag⁺ ions were reduced to silver nanoparticles with their subsequent introduction into the PLA (mechanical method) and Ag⁺ ions were reduced in the polymer matrix of PLA-AgPalmitate (PLA-AgPalm) (in situ method). Structure, morphology and thermophysical properties of nanocomposites PLA-Ag were studied by FTIR spectroscopy, wide-angle X-ray scattering (WAXS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) methods. The antimicrobial, antiviral, and cytotoxic properties were studied as well. It was found that the mechanical method provides the average size of silver nanoparticles in the PLA of about 16 nm, while in the formation of samples by the in situ method their average size was 3.7 nm. The strong influence of smaller silver nanoparticles (3.7 nm) on the properties of nanocomposites was revealed, as with increasing nanosilver concentration the heat resistance and glass transition temperature of the samples decreases, while the influence of larger particles (16 nm) on these parameters was not detected. It was shown that silver-containing nanocomposites formed in situ demonstrate antimicrobial activity against gram-positive bacterium S. aureus, gram-negative bacteria E. coli, P. aeruginosa, and the fungal pathogen of C. albicans, and the activity of the samples increases with increasing nanoparticle concentration. Silver-containing nanocomposites formed by the mechanical method have not shown antimicrobial activity. The relative antiviral activity of nanocomposites obtained by two methods against influenza A virus, and adenovirus serotype 2 was also revealed. The obtained nanocomposites were not-cytotoxic, and they did not inhibit the viability of MDCK or Hep-2 cell cultures.

Recently, nanocomposite materials containing nanoparticles of metals such as silver, copper and zinc oxide have attracted most attention due to their pronounced pharmacological properties, such as antimicrobial, antiviral, antiinflammatory, immunomodulatory ability and high stability in extreme conditions. Polyelectrolyte complexes based on polymers of natural origin, namely polysaccharides of chitosan and pectin, which can stabilize nanoparticles of a smaller size than individual polymers have significant potential for creation of silver-containing nanocomposites. The aim of this article is to study the antimicrobial and antiviral activity of silver-containing nanocomposites based on polyelectrolyte complexes. Methods. Peculiarities of the structural organization of silver-containing nanocomposites were investigated by the method of wide-angle scattering on an XRD-7000 diffractometer. The morphology of Ag nanoparticles in polymer matrixes were studied by transmission electron microscopy method (transmission electron microscope JEOL 100 CXII). The antimicrobial activity of silver-containing nanocomposites was determined by agar diffusion assays against opportunistic pathogens Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. Cytotoxicity and antiviral activity were investigated using the MTT method and staining by gentian violet. Results. Analysis of wide-angle X-ray diffractograms of silver-containing nanocomposites based on polyelectrolyte complexes Na-CMC (pectin) – chitosan showed that at reduction of Ag+ ions to metallic silver, there are two low-intensity diffraction maxima at 2θm ~ 380 and 440 in the diffractograms. These maxima correspond to the crystallographic planes of the face-centered cubic lattice of silver, are characterized by indices (111) and (200), respectively, and confirm the presence of metallic silver in the polymer system. Analysis of micrographs of silver-containing nanocomposites based on Na-CMC and chitosan showed that larger nanoparticles are formed with increasing the molecular weight of chitosan. The dependence of the size of silver nanoparticles on the wavelength of ultraviolet radiation at reduction of silver ion in polyelectrolyte-metal complexes Na-CMC–Ag+–chitosan of low molecular weight was also revealed. In particular, smaller particles are formed under irradiation by light with a shorter wavelength (λ =254 nm) than at λ=365 nm. Silver-containing nanocomposites Na-СMC-Ag-chitosan and pectin citrus-Ag-chitosan, obtained by reduction of Ag+ ions under ultraviolet irradiation at a wavelength λ = 365 nm and λ = 254 nm, exhibit high antimicrobial activity against the test cultures of microorganisms S. aureus, E. coli, and P. aeruginosa C. albicans. No significant dependence of antimicrobial activity on the molecular weight of the studied samples was noted: the obtained data were within close limits and had close values. In addition, no dependence of antimicrobial activity on the type of investigated test cultures of microorganisms was observed either. Nanocomposites based on Na-CMC-chitosan (λ = 365 nm) inhibited infection titer HSV-1 by (3.72–5.45) lgTCID50/mL, whereas the decrease in titer during incubation with samples based on citrus pectin-chitosan was within (2.39–2.42) lgTCID50/mL. A dose-dependent relationship between molecular weight of chitosan and reduction of infection titer was observed. It was found that silver-containing nanocomposites formed by reduction of silver ions in polyelectrolyte-metal complexes under ultraviolet radiation of different wavelengths had no cytotoxic effect on cells of MDCK and BHK. Conclusions. The investigated silver-containing nanocomposites based on Na-CMC (pectin)-chitosan polyelectrolyte complexes show antimicrobial activity against test cultures of S. aureus, E. coli P. aeruginosa, and C. albicans along with antiviral activity against herpes simplex virus type 1 and influenza virus. It was established that the obtained nanocomposites did not show a cytotoxic effect on MDCK and BHK cells. The obtained data allow us to assert that investigated silver-containing nanocomposites are promising antimicrobial means for the development of new effective strategies against microorganisms and viruses and improvement of the population health.

Food quality and safety issues are among the most pressing and important for manufacturers, retailers, and end consumers. However, the development of pathogenic microorganisms in such products not only reduces their shelf life but also causes the development of infectious diseases in consumers. Therefore, there is currently an urgent need to find new packaging materials with antimicrobial effects that are non-toxic to humans, food, and the environment. The aim of this article is to study the antimicrobial activity of silver-containing nanocomposites formed based on polylactide (PLA) and polycaprolactone (PCL) with silver nanoparticles by sputtering deposition. Methods. The structure of silver-containing nanocomposites were investigated by the method of wide-angle X-ray diffraction on an XRD-7000 diffractometer. The morphology of Ag nanoparticles on the surface of the films was studied by transmission electron microscopy method. The antimicrobial activity of silver-containing nanocomposites was determined by agar diffusion assays against opportunistic pathogens S. aureus, E. coli, P. aeruginosa, and C. albicans. The study of the impact of packaging biopolymer materials with silver nanoparticles on the total number of mesophilic aerobic and facultatively anaerobic microorganisms, bacteria of the Escherichia coli group, mold and yeasts in food products, were studied by DSTU for 30 days. Results. The presence of metallic silver on the PLA-PCL film surface was confirmed by wide-angle X-ray diffraction. This is indicated by the presence of two low-intensity maxima at 2θm ~ 380 and 440 in the diffractograms of the samples. These maxima correspond to the crystallographic planes of the face-centered cubic lattice of silver, are characterized by indices (111) and (200), respectively, and confirm the presence of metallic silver on the surface of the polylactide-polycaprolactone film. The analysis of the micrographs of the nanocomposites showed that when silver nanoparticles were sputtered on the surface of the PLA-PCL polymer matrix, a layer with a thickness of about 425 nm was formed. It was found that the prepared biopolymer packaging materials PLA and PLA-PCL with Ag nanoparticles sputtered for 3 and 5 min showed antimicrobial activity against S. aureus and E. coli and were inactive against B. subtilis and P. aeruginosa. Packaging bakery products in biopolymer films helps reduce the loss of crumb moisture during storage, slows down the loss of hydrophilic properties, and reduces fragility, which helps extend the shelf life of fresh bread. The moisture content in packaged pumpkin seeds remained stable for two months at the control level. It was found that in wheat bread (for 7 days) and pumpkin seeds (for 30 days), packaged using all types of packaging material PLA-PCL, PLA-PCL-Ag, and conventional PA/PE vacuum film throughout the experiment, no quantitative changes in MAFAnM microorganisms, yeasts, and molds were observed. Studies of the antimicrobial effect of the biopolymer packaging material PLA-PCL-Ag have demonstrated the quality and safety of the films produced, as the calculated values of the total number of microorganisms, yeast and molds, in particular, meet the standards of DSTU. Conclusions. The data obtained suggest that the formed biopolymer packaging materials have antimicrobial properties and are promising for use in the food industry for food packaging, which can extend the shelf life of various product groups without alteration in quality and safety indicators.